how can i check login details stored on server on iphone

Hello friends,

I am newbie and just started working with sencha touch...i am trying to create login page.
I have DB on server and when user enters username and password and submits form i want to check username and password against details stored on server using ajax or traditional form submit.
If its a simple web application i would have used CURL or something...how can i do it in sencha touch. i mean i cant call file like this